Presses – Methods – With heating or cooling
Patent
1997-11-24
1999-06-01
Gerrity, Stephen F.
Presses
Methods
With heating or cooling
100 90, 100207, 100301, 100319, 100320, 100323, 100325, 523149, B30B 1534, F16D 6904
Patent
active
059079959
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for thermally treating surfaces of friction linings by pressing against a heated plate in a scorch press and a scorch press for carrying out this method.
BACKGROUND OF THE INVENTION
Friction linings, particularly organically bonded friction linings, are nowadays frequently subjected to high thermal loading. Since they are supposed to produce a high braking force, even in the first braking process, the friction surface is thermally treated by pressing it against a hot plate (scorching) or with a gas flame or the like in order to prevent green fading (DE-A 4032182). The decomposition products of the organic bonding agent in the region close to the surface, which are responsible for the reduction in the coefficient to friction, are thus removed.
In the scorching process, e.g. 20 ground and post-hardened friction linings are pressed simultaneously against a hot plate at up to 750.degree. C.
The heating process can be interrupted a number of times by ventilation in order to facilitate the removal of the decomposition products. The linings are subsequently cooled by pressing against a cooling plate. The back plates of the friction linings are then generally cleaned and coated.
It is disadvantageous in the known method that the friction surface is subjected to the maximum temperature even when it is pressed for the first time against the heating plate. Sealing of the surface can thereby occur which prevents the escape of the decomposition products. The temperature of the heating plate can also be maintained constant over its entire area only with great difficulty. Temperature variations of 15K and more are quite common. The friction linings of a scorched batch can thus have a different wear or coefficient of friction.
The treatment time for the scorching is naturally dependent on the shape and material of the friction lining, it is thus practically impossible to integrate the known scorching process into a continuous manufacturing method.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION
It was thus the object to make a continuous thermal treatment of friction lining surfaces possible in which all the friction linings are treated with predetermined cycle times under the same conditions.
The object is solved if the friction bearings are supplied after hardening directly to the scorch press without significant cooling, if the friction linings are treated in the scorch press in a number of stages, each treatment stage lasting for a cycle period and including a transport phase and a pressing phase, the surface of the friction linings being pressed in the pressing phase against a respective thermally operative plate and the friction linings being pressed in a first pressing phase against a hot heating plate at up to 900.degree. C. and, in a subsequent pressing phase, against a cooling plate.
The friction linings are preferably pressed with a pressing force of 50-5000 daN. Relatively high pressing forces effect no further improvement in the thermal transfer whilst an impaired thermal transfer must be tolerated at lower pressing forces. The transport phase corresponds to the ventilation phase in the known process.
Since the individual thermal treatment and cooling stages are performed in different modules of the scorch press, the temperature of each thermally operative plate and the pressing force in each stage can be set optimally in dependence on the shape of the linings and the composition of the friction composition. The friction surface can thus be heated or cooled in each stage to the temperature of the heating or cooling plate. The entire temperature variation with time at the friction surface may thus be controlled and sealing prevented. Furthermore, energy is saved by this temperature control. As a result of the splitting up into different heating modules, it is also simpler to maintain the surface temperature constant over the entire heating plate so that the deviations are at most 1K.
The cycle period is generally 3 to 60 s. 0.5 to 2 s are apportioned t
REFERENCES:
patent: 2661789 (1953-12-01), Keller
patent: 2662960 (1953-12-01), Williams
patent: 3014520 (1961-12-01), Myers
patent: 3505446 (1970-04-01), Griffith
patent: 4187777 (1980-02-01), Pringle
patent: 4543147 (1985-09-01), Noto et al.
patent: 5080969 (1992-01-01), Tokumura
patent: 5141586 (1992-08-01), Myers et al.
Jenniges Norbert
Lauth Oliver
Steinkamper Ulrich
Zimmer Thomas
Gerrity Stephen F.
Rutgers Automotive Aktiengesellschaft
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